Q1_Aircraft: onan

i was able to get an a&p / aironotical engineer named bob clark to
come over to see the kit i had just picked up to give me a few
pointers on repairs to make and directions to head from here. i
believe he had his q1 flying in 1980 (he is briefly mentioned in one
of the newsletters). mr. clark was a big fan of the onan with a
modified pitch prop. one bit of advice i gleaned from him regarding
the onan was the exhost. he, like most peope, initially had problems
with vibration. to solve the vibration problem he used a 7/16' exhost
equalizer tube to connect the two exhost pipes togeather near the
head. he claimed that this made the engine run pretty smooth. anyone
else heard about this trick?

rocky

Rocky,

Actually the problem is due to more than that.

Whenever you have a boxer engine in which the cylinders are not in
line you will get vibration because of the unbalanced forces. it is
due to a situation called a couple.

Think of a H shape with an arrow head on two diagonally opposite
legs (which are the forces due to the power strokes), remove the
other two legs and you will get the picture.

Quickie tried to compensate with a rotating mass on the prop
extension (the lug.) This was partially successful but incomplete.
Couples need to be corrected with couples. ( not to be confused with
marriage counselling...)

We took the engine to a balancer and said, 'make it better'. He did
this by adding another bolt on eccentric lug to the flywheel
diametrically opposite to the prop flange lug. That helped a lot,
it still shook but the levels of discomfort dropped considerably.

More could have been done to smooth it at the cruise RPM, but other
things got in the way of further development.

I may be able to rustle up a photo if anyone is interested.

John


--- In This email address is being protected from spambots. You need JavaScript enabled to view it. , 'fuddworks' <rockaford99@h...>
wrote:
>
> i was able to get an a&amp;p / aironotical engineer named bob clark to
> come over to see the kit i had just picked up to give me a few
> pointers on repairs to make and directions to head from here. i
> believe he had his q1 flying in 1980 (he is briefly mentioned in
one
> of the newsletters). mr. clark was a big fan of the onan with a
> modified pitch prop. one bit of advice i gleaned from him
regarding
> the onan was the exhost. he, like most peope, initially had
problems
> with vibration. to solve the vibration problem he used a 7/16'
exhost
> equalizer tube to connect the two exhost pipes togeather near the
> head. he claimed that this made the engine run pretty smooth.
anyone
> else heard about this trick?
>
> rocky
>